Effect of 1,25-dihydroxycholecalciferol on glucose metabolism in gestational diabetes mellitus

The effect of 1,25-dihydroxyvitamin D supplement on glucose metabolism was evaluated in 12 women with gestational diabetes mellitus (GDM). All women had an oral glucose tolerance test (OGTT) performed at inclusion in the study. Thereafter, each patient was instructed to continue their normal diet during the following 2 days, after which they received 2 micrograms/m2 Etalpha i.v. 2 h prior to the second OGTT. During the next 14 days each patient received 0.25 microgram Etalpha orally, after which a third OGTT was performed. On average the level of 1,25-dihydroxyvitamin D3 at inclusion at baseline significantly increased after i.v. 1,25-dihydroxyvitamin D3 (from 92 to 138 ng/l [p < 0.001]), but returned to the baseline level after 2 weeks of oral Etalpha (85 ng/l). Simultaneously, the glucose level decreased from 5.6 to 4.8 mmol/l (p < 0.01) after i.v. treatment with 1,25-dihydroxyvitamin D3, but did not differ significantly from inclusion following 2 weeks of oral Etalpha. There was no difference between the glucose concentrations during OGTT prior to and after i.v. or oral 1,25-dihydroxyvitamin D3, in contrast to the insulin levels which tended to be lower after both i.v. and oral supplementation. In a multiple regression model including 1,25-dihydroxyvitamin D3, insulin, weight and height against glucose, only 1,25-dihydroxyvitamin D3 and insulin were selected for the final model (r2 = 0.73, p < 0.0001). Our results suggest that supplements of 1,25-dihydroxyvitamin D3 influence glucose metabolism in patients with GDM probably by increasing the insulin sensitivity.